Gilead Sciences Inc. launched a Phase II/III clinical trial of its orallyadministered nucleotide analogue, which is a reverse transcriptaseinhibitor, for treatment of AIDS.

In two Phase I/II studies, the Foster City, Calif., company said thedrug, GS 840 (adefovir dipivoxil) demonstrated it was well toleratedand achieved improvements based on two standard surrogate markersused to judge anti-HIV drug performance _ an increase in CD4counts and decrease in viral load.

Lana Lauher, Gilead spokeswoman, said the Phase I/II study will take12 to 18 months to enroll 400 patients, who first will receive 24weeks of treatment under placebo-controlled conditions and thencontinue taking GS 840 for another 24 weeks in an open-labelsetting.

Those HIV patients participating in the trial will have CD4 countsbetween 200 and 500 and will continue to take other antiviral drugs.Endpoints for the study will assess GS 840's ability to boost CD4counts and reduce viral load.

Because patients will be receiving a combination of AIDS drugs, theGilead study could evaluate the performance of GS 840 takentogether with nucleoside analogues and protease inhibitors.Nucleoside analogues also are reverse transcriptase inhibitors andwere the first AIDS drugs on the market. Protease inhibitors are thenewest class of FDA-approved AIDS drugs.

The reverse transcriptase inhibitors attack HIV in the beginning of itsreplication cycle while the protease inhibitors strike near the end.

The main differences between Gilead's nucleotide analogue and anucleoside analogue is that the former already is activated, ready tofight the virus, as it enters immune system cells, whether they areinfected with HIV or not and whether they are in the process ofdividing. Nucleoside analogues have to be activated, either by viralor cell replication.

Lauher said GS 840 has a dosing advantage over other HIV drugs.Patients receive one small tablet, once a day, rather than multipletablets several times each day.

The nucleotide also is being evaluated in a Phase I/II trial in the U.K.for hepatitis B infection.

Gilead's lead compound is Vistide (cidofovir injection), anothernucleotide analogue, which is under review by the FDA for treatmentof cytomegalovirus retinitis in AIDS patients.

Gilead's stock (NASDAQ:GILD) closed Wednesday at $33.50, down75 cents. n

-- Charles Craig

(c) 1997 American Health Consultants. All rights reserved.